Find Out How Prince William Is Spending His Birthday!

The soon-to-be father isn't celebrating his 31st birthday quite how one might expect. The young royal was spotted arriving at Alnmouth for his close friend Lady Melissa Percy's wedding, which is set to take place over the weekend.

The Duke of Cambridge will serve as the best man at the nuptials, although he missed out on the rehearsal dinner this afternoon, a source told E! News.